bap8guy | BK1801 20Hz to 40Mhz Frequency Counter @bap8guy | Uploaded June 2022 | Updated October 2024, 20 hours ago.
This is a nice example of a working BK1801. It is in nice condition both physically and operationally. The 1801 is expected to cover 20Hz to 40Mhz, but as this video demonstrates, it is capable of comfortably performing up to 60Mhz, with 50Mhz being a nice working maximum.

This unit will be accompanied by a CD service manual.